Fractionating column



l 6, 5, 9 3 2 um U R Rim U I Dm m E Jan. 1s, 1944. y

4 Sheets-Sheet 1 I Filed may 27; 1941 Jan. 1s, 1944. E, BURR@ 2,339,561

FRACTIONATING COLUUR Filed lay 27. 1941 4 Sheets-Sheet 2.

, Jan 18, 1944. E. l... DURRUM u 2,339,561

FRACTIONATING COLUMN Filed May 27., 1941 v 4 Sheets-Sheet 3 l bq his AHornzq- Patented Jan. 18, 1944 FRACTIONATING COLUMN Emmett L. Durrum, San Francisco, Calif., as-` signor to -Shell Development Company, San Francisco, Calif., a corporation of Delaware Application May 27, 1941, Serial No. 395,382

9 Claims.

The present invention relates to improvements in bubble tray columns, used in fractional distillation, stripping, absorption, etc. More particularly, it relates to improved bubble trays which are of simple construction and high eniciency.

In the past, it has been customary to equip bubble columns with bubble trays made up of numerous elements comprising, among others, individual risers and bubble caps. These ele'- ments are of such nature that they must be secured in place to thev bubble tray by welding or other means and the fabrication of such trays requires large amounts of time and labor. In some cases, especially when dealing with certain materials, such as glass or plastics, the labor and technique of fabrication and assembly are such that bubble trays according to the old plan could be made eithernot at all or only under such difculties as to make their fabrication as a practical matter totally impossible. this, conventional bubble trays, which are welded or otherwise fastened in towers, have the drawback that at the temperatures of operation they warp or even crack loose from the column due to stresses set up by unequal thermal expansionor contraction at operating temperatures.

It is an object of the present invention to provide a simple inexpensive bubble tray. It is another object to provide a bubble tray which is an expansible member and which is adapted to be readily fabricated from glass, plastics or metals by molding, casting, forging, stamping, etc. It is a further object to provide a bubble tray eliminating the conventional risers and bubble In addition tocaps. Other objects will become apparent from reading the present specication.

The present invention comprises a bubble tray provided with downspo'ut means comprising two plate elements arranged to co-act .to provide a liquid seal upon the tray. The top plate element according to the present invention is formed to provide a plurality of raised portions thereof, near the bases of which perforations are provided through the plate. The bottom plate element is likewise' composed of corresponding raised portions adapted to register with the raised portions of the top plate. Perforations are provided through Vthe bottom plate within the area of the raised portion. The plate elements are so disposed with respect to each other that the openings in .the bottom plate element are at a level above the openings in the `top plate element and in this manner a liquid seal may be maintained upon the tray. The invention can be better understood from a consideration of the drawings. l

Figures I to V are views of one type of bubble tray embodying the essential elements of the invention.

Figure I is a quarter perspective view of a portion of the bubble tray with parts broken away. Figure II is a top plan of a section of a bubble column equipped with said tray.

Figure III is a sectional elevation of a column showing two trays, including downspouts and i their disposition with respect to each other.

Figure IV is a bottom plan of said column.

Figure V is a quarter elevation showing detail of a preferred type of top plate trough.

Figures VI to IX are views'of another type of bubble tray according to my invention wherein the length ofthe path of liquid flowing across the plate is increased.

Figure VI is a top plan of a section of column employing this type of tray and is taken on line VI--VI of Figure VII at the point indicated thereon looking in the direction of the arrows.

Figure VII is a sectional elevation of a column showing three trays including downspouts and their disposition with respect to each other.

Figure VH1 is a bottom plan section taken on line VIII-VIIIof Figure VII at the point indicated thereon looking in the direction of the arrows.

Figure IX is a quarter perspective View `of a portion of the bubble tray. l '-,I`

Figure X is a top view of a tray in which the elevated portions are arranged concentrically and parallel.

Figure Xl is a cross section of a portion of the tray of Figure )HI taken at the points indicated thereon looking in the ydirection of the arrows.

Figures XII to XIV are views of another type l' of bubble tray according to thev present invention, wherein the spiral does not lie in a single horizontal plane.

Figure XII is a sectional elevation of a coluinnv lshowing trays of this type and their relationship to each other.

Figure XIII is a top plan of the peripheralv Figure XIV is another top plan of the peripheral downspout system of Figure XII .taken at the points indicated thereon looking in the direction of the arrows.

, In Figure I, 20 represents the bottom plate ele-- ment which comprises a single Asheet of metal,

provided in crests 24.

Top plate element 30 likewise comprises a sinl gle sheet formed inthe manner shown to produce corresponding annular concentric troughs 32 and crests 34. The troughs 32 in their lower portions are provided with perforations 36.

It is important that periorations 28 in bottom plate are at a higher level than the corresponding perforations 36 in top plate in order that a liquid seal may be maintained upon the tray.

The top plate element 30 may be, fastened to bottom plate element 20 in any suitable manner, such as by welding, bolting, riveting, etc., at appropriate points, such as welding plate 30 to plate 20 at the periphery oi the former, or bolting plate 20 and plate 38 at points along 324 and 22 with or Without spacers (not shown) to maintain a vertical clearance between these portions of plate elements 20 and 30, as explained below.

In Figure l1, 38 represents the column wall to which is fastened the bottom plate element 20 by welding or other suitable means. Plate element 20 is provided with downspout 40, andcarries top plate element 30 described above.

In Figure V, troughs 32 are provided with perforations 36 which may vary in size and are disposed in such manner that the jets of gas emergingtherefrom do not converge, and in which the perforation sizes vary to make allowance for differences in pressure with respect to their height. When employing top plate elements with perforations of this type, it is preferable that there be some clearance between the crests 24 of plate 20 and the troughs 32 of plate 30, in order that there is a gas passage to the bottom holes 36.

In operation of a column built upon this plan, liquid collects above the trays at a level determined by the level of the edge of downspout 40 above the tray and flows from the point of entrance below the downspout from the plate above,

' across the plate through downspout 40' to the plate below. The vapors or gas pass up the column through perforations 28 and 36 in the plates, thus forming jets of gaswhich intimately contact the liquid as it iiows across the plate. The height of the edge of downspouts 40 and 40' above the level of the tray has been exaggerated in Figure III for purposes of simplicity and to indicate clearly that a liquid seal is present. However, in practice, except when dealing with high vapor velocities, the level of the downspout 40 would be about the same as, or only slightly higer than, the level of the perforations 28 in the bottom plate. Gas is prevented from owing up through the downspouts by the fact that they terminate at a point beneath the liquid level of the tray which they feed.

In Figure VI, which represents a top view of another typeof tray according to the present inventionI (B of' Figure VII represents the tray described herein except where otherwise indicated) 42 represents the top plate element which comprises la single sheet of metal, glass or other material, formed in the manner shown to produce parallel spiral troughs 44 and crests 46 originating near the center and terminating near the' periphery of the tray, provided with downspout 48. Perforations 58 are provided in the troughs 44 (for simplicity, only a portion of these perforations 48 have been indicated). Plate element 42 is fastened to column wall52 in any suitable manner. 54 represents the area upon the tray B where the liquid from the tray A above enters the tray B through the downspout bounded by wall 56, dam 58, column wall 52 and spiral baille 60.

Spiral baiiie 60 is fastened to the crests as shown by spot welding or other means, o ne end being fastened to downspout 48 while the other is fastened to column wall 52 at point 62. 'I'hus baille 60, plate 56 and column wall 52 bound area 64.

In Figure VII area 66 is cut from downspout 48 so that the upper portion is the same height as baiiie plate 68 while the distance between the tray and the edge of the lower portion of the cut serves as-a dam to regulate the depth of the liquid maintained on the tray. Area 61 is cut from the bottom of downspout 48 to admit liquid from the tray above and to direct the flow into the spiral path. The rest of the bottom edge of downspout 48 contacts the plate it-'feeds and may be fastened thereto, if desired, although this is generally not necessary.

It may be observed that the center of the plates is alternately the downspout or the receiving area, depending upon its relationship to the plate above. In plate A the central area 68 is not cut out, but the area 54 at the periphery is cut out to carry the downspout bounded by and comprising column wall 52, dam 58 and a vertical extension (not shown) of Aspiral bame 60 between wall 56 and dam 58 and a vertical extension (not shown) of wall 56, whilein plate B the central area 66 is cut out to carry downspout 48 while the liquid is admitted to the plate or area 54 which is solid, and thus there is no vertical extension of wall 56 or the portion of spiral baille 60 between 56 and 58. Tray C is similarto tray A, etc. Weep holes 10 are provided at the base of plate 56 to drain to the downspout any liquid collected in area 64. Upon trays which have the central area cut out (e. g., B) wall 56 may be dispensed with entirely if desired.

In Figure VIH, which is a bottom view of tray B (as of Figure VII), 52 represents the column wall to which is attached bottom plate element 12, which likewise comprises a single sheet of material, formed in the manner shown to pro duce a series of parallel spiral troughs 14 and crests 16. The crests 16 are provided with perforations such as slots 18. The area 68 is cut out to carry downspout 48. The dotted line represents theportion cut out in case the tray were one higher or one lower than shown (that is, A or C as of Figure VII). In the latter case, the central portion 68 is left solid. l

In operation of a tray built according to this type, the liquid condensate collects upon the tray and ows in a spiral path over the tray as the gases `or vapors bubble through it. The liquid level is maintained about at the level of the crests by the dams, although the'foam above it may be 2 to' 3 times or more higher. The baille 68 forces the foam as well as the liquid to follow the elongated spiral path. The object of increasing the length of the path of ow across the tray is to increase the degree of `contact and fractionation eiciency. The liquid flows across one tray A down through the downspout at the periphery to the periphery of the tray below B along the spiral path to the center of the tray,-

. I|8 near their bases.

center, to the center of the tray below to its periphery, etc., other types of flow, such as from periphery to center, to the periphery of the tray below to the center of that tray, etc., can be used by a suitable downspout system without departing from the spirit of the present invention. Likewise, it is within the scope of this invention to reverse the spirals of alternate trays or to vary the differences in distance between trays, as desired.

In Figure X top plate element 80 is provided with downspout apertures B2 and individual elevated portions 84 provided with perforations 86.

Figure XI shows a cross section of the tray of Figure X in which the bottom plate element is represented by 88 and .a perforation therein by 90 In Figure XII, 92 represents the column wall to which is attached upper plate element 94. Plate element 94 comprises a single sheet formed in the manner shown to provide spiral raised crests 9G and troughs 98, provided with perforations near the bases vof the troughs. The spiral troughs descend from the apex around an imaginary cone terminatingin a downspout at the periphery as indicated.

Upper plate 94 carries lower plate |02 comprising a corresponding spiral cone provided with crests |04 and troughs |06, registering with the.

corresponding crests and troughs of the upper plate. Crests |04 are provided with perforations |08. Plate elements 94 and |02 co-act to form tray A.

Tray B comprises top plate' element ||0 and bottom plate element I2. Top plate element H0 is fastened to column wall 92 and likewise comprises a series of crests ||4 and troughs H6, the latter of which are provided with perforations Plate element ||0 carries bottom plate element ||2, which comprises corresponding spiral troughs and crests and |22, respectively. IlLhe crests are provided with perforations |24. The spiral troughs in tray B originate at a point directly under the downspout of plate A at the periphery and descend around an imaginary inverted cone, terminating at the apex.

In top plate element'l 94, at the point where the spiral trough fades into the column wall, is provided an opening for a downspout, comprising wail |26 and end plates |28 and |30 (see Figures XIII-XIV) which, with wall 92, bound the downspout and terminate at the bottom in opening |32. On lower top plate element ||0 are provided dams |34 and |36 to provide a seal for the downspout of the plate above. Plate element ||0 is also provided with a central downspout pipe |38, which may be an integral part of plate elements I I0, at the terminus of the spiral trough at the central lower portion of the cone tovfeed the plate below.

In normal operation of a tray built according to this type, liquid reflux is fed upon the apex of the tray A and flows in a spiral path down over the tray as the ascending gases or vapors bubble through it. The liquid flows from the center of one tray around a descending spiral to the periphery, down through the downspout to the pe riphery of the tray below, around in a spiral, terminating at the center and thence to the center of the tray below to its periphery, etc. A column of this type is especially useful when dealing with high reflux ratios and it is important that sucient liquid head be maintained so that the liquid does not run away from the heights to the lower portions of the tray, leaving free gas passage without the necessity of bubbling the vapor through liquid. Gas is forced to pass up through the liquid and not up the downspouts by the seals provided at the points where the downspouts terminate in the plates below.

Although the drawings show that the spirals encompass a cone, it is only necessary that the origin of the spirals and their terminals be upon different levels, so that the flow by going downward is accelerated to overcome fluid friction. Likewise it is notvnecessary that the alternate cone-like spiral plates be inverted, since with a suitable downspout system they may be all disposed in the same manner.

The tray construction of the present invention is adapted for use in any type bubble tower or fractionating tower consisting of a vertical and preferably cylindrical vessel, varying in diameter and height according to the specific work to be done, the volume of vapors to be handled and the degree of fractionation necessary.

A bubble or fractionatng tower is equipped either centrally or near its lower portion 'with a vapor inlet line and a vapor outlet line near the top of the tower. Means may be provided for the supply of liquid condensate to the `top of the tower or closed coils may supplement the trays to increase fractionation of the vapors. In the bottom of the tower is a liquid draw-olf line.

Of the above, details with reference to operat? ing requirements of the tower itself have been eliminated from the drawings for simplicity, since the structural requirements for bubble towers have long been well known to the art, particularly with reference to the fractionation of oils, alcohols, etc. v Although no drawing shows more than three trays, it will be understood that any number of trays may be positioned in the tower according to the requirements of a particular installation. In some of thedrawings, forvsimplicity a por-- tion of the perforations has not been shown. It is to be understood that perforations are rdistributed all over the trays infaccordance with the invention.

In general, it is preferable that the trays should top plate perforations from 7% to 15% of this area. It is understood, however, that substantial variations from these gures may be required for special cases.

The optimum depth of the liquid upon the tray depends upon the vapor velocity through the column and in general the higher the vapor velocity the greater the depth of the liquid that should be maintained upon the tray. Under ordinary cir` cumstances a liquid level approximately the same as the level of the perforations in the bottom plate is satisfactory. I

Although only two variations of cross tray flow have been shown, that is, flow from periphery to periphery with an axis parallel to the diameter and `spiral ow, it is to be understood that other baille systems may be employed to increase the vlength of the path of flow across the plate. However, this type plate construction is especially well adapted to spiral flow and such a spiral tray is a preferred modification of the present invention. Y

Although the baille 60 has been represented in the drawings as a separate piece of metal fastened to the crests 46, it is to be understood that the invention also contemplates bales which are integral parts of the plate elements comprising raised portionswhich are higher than adjacent crests.

Another advantage of the spiral or concentric trough and crest construction is the ability of such members to withstand tendencies to buckle and warp clue to thermal expansion and contraction that occur with changes in temperature.

When dealing with spiral trays according to the present invention, it is best that the length of the spiral path be not greaterthan aboutten times the diameter. Otherwise, pressure drop due to frictional resistance of flow across the tray may be suiiicient to cause channeling. Spirals of approximately the proportions shown in the drawings, wherein the path is between about 4 and 6 diameters, are preferred, the drop in presl sure due to friction being practically negligible and no channeling occurring.

Although the plate elements of my bubble trays, as described, may be fabricated in several pieces, for example, in halves, quarters, sixths, etc., and these parts welded, bolted, or otherwise fastened together, sometimes it is preferable to fabricatc the entire plate element as a whole to cover the entire cross sectional area of the column.`

In this case the trays produced are of extremely simple construction, consisting of but three elements, a downspout (the portion of which extends above the plates serving as a dam to regulate the depth of liquid upon the tray), and the co-acting bottom and top plate elements. bottom plate elements of such a tray can be stamped, cast, molded, drop or hydraulic forged, in one operation and the entire tray be completed by simply fastening the top element to the bottom element and welding or otherwise fastening the downspout in the aperture provided.

In cases where the raised elements are parallel, the tray can be fabricated by bending either with or without the application of heat and the trough ends covered by fastening a separate sheet of metal thereon.

Trays according to the present invention are especially well adapted to be cold stamped from4 relatively thin sheet metal. Trays can be made up to 4 feet o r more inA diameter of suflicient strength to withstand all the stresses of ordinary operation, although, if desired, supporting members such as angle irons and the like can be used to reinforce them. This is especially desirable with trays of larger diameter. By stamping heated metal sheets or forging, considerablyV thicker -plates may be used.

The present invention has been described with the aid of simplified drawings; however, it should be understood that it may be embodied in other forms without departing from the spirit thereof. This is especially true with regard to the arrangement, distribution, size, shape, depth and contour of the raised portions upon the plate elements and the materials from which they are made; and also with respect to the distribution, size and shape of the perforations therethrough. It is only necessary that the top plate elementsand the bottom plate elements be vmade of continuous sheets and be provided with elevated portions which correspond in arrangement although they 1 may diier in shape and are so positioned that the perforations at the lowest level in the bottom plate are at a higher level than the corresponding perforations at the highest level in the top plate,

The top and so that a liquid seal may be maintained upon the plate.

I claim as my invention:

1. In a bubble column a bubble tray comprising a continuous top plate element and a continuous bottom plate element, said elements being formed to provide a series of corresponding alternate crests and troughs arranged in banks around a centrally located point of said tray, said top plate element being superimposed on said bottom plate element so that said crests .and troughs are in vertical alignment, said top plate element having perforations therethrough within the areav of said crests, and said pc rforations in said crests are at a higher lever than said perforations in said troughs.

2. In a bubble column a bubble tray adapted to compensate for thermal expansion and contraction comprising a continuous top plate element and a continuous bottom plate element, said elements being formed to provide a series of corresponding concentric crests and troughs, said top plate element being superimposed on said bottom plate element so that said crests and troughs are in vertical alignment, said top plate element having perforations therethrough within the' area of said troughs, said bottom plate element having perforations therethrough within the area of said crests, and said perforations in said crests are at a higher level than said perforations in said troughs.

3. In a bubble column a stamped bubble tray comprising a continuous top plate element and a continuous bottom plate element, said elements being stamped'to provide a series of corresponding alternate crests and troughs arranged in banks around a centrally located point of said tray, said top plate element being superimposed on said bottom plate element so that said crests and troughs are in vertical alignment, said topA plate element having perforations therethrough within the area of said troughs, said bottom plate element having perforations therethrough within the area of said crests, and said perforations in said crests are at a. higher level than said perforations in said troughs.

4. In a bubble column a bubble tray comprising a continuous top plate element and a. continuous bottom plate element each of said elements being cold stamped from a single sheet of 16 gauge or thinner gauge metal to provide a series of corresponding alternate crests and troughs arranged in banks around a centrally located point of said tray, said top plate element being superimposed on said bottom plate element so that said crests and troughs are in vertical alignment, said top plate element having perforations therethrough within the area of said troughs, said bottoml plate element having perforations therethrough within the area of said crests, and said perforations in said crests are at a higher level than said perforations in said troughs;

5. In a bubble column a. bubble tray comprising a top plate element and a bottom plate element, said elements being formed to provide a series of corresponding spiral shaped alternate crests and troughs originating near the center and terminating near the periphery of said tray, said top plate element being superimposed on said bottom plate element so thatl said crests and troughs are in vertical alignment, said top plate element having perforations therethrough within the area. of said crests and said bottom plate element having perforations therethrough within the area of said crests, and said -perfora- 6. In a bubble column a bubble'tray comprising a top plate elementv and a bottom plate element, said elements. being-formed to provide a series of corresponding spiral alternate crests and troughs originating near the center and terminating near the periphery of said tray, said top plate element being superimposed on said bottom' plate element so that said crests and troughs are in vertical alignment, said top plate element having perforations therethrough Within the area of said troughs, said bottom plate element having perforations therethrough within the area of said crests, and said perforations in said crests are at a higher level than said perforations .in vsaid troughs, and a corresponding vertical spiral baille aligned in conformity with said spiral crests and troughs and fastened thereto. l Y

7. In a bubble column of circular cross-section tray comprising a top plate element and a bottom plate element, said elements forming a series of corresponding spirall crests and troughs originating near the center and -terminating near the periphery of said tray-to provide a spiral path for liquid, said top plate element being superimposed on said bottom plate element so that said crests and troughs are in vertical alignment; said top plate element having perforations therethrough within the area of said troughs, said bottom plate element havingperforations therethrough Within the area of said crests, and

the length of said path being not greater than 10 diameters of said tray.

8. In a. bubble column a bubble tray comprising a continuous top plate element and a continuous bottom plate element, said elements being formed to provide a series of corresponding spiral alternate crests and troughs originating near the center and terminating near the periphery of said tray, said top plate element being superimposed on said bottom plate element so that said crests and troughs are in vertical alignment, said top plate element having perforations said perforations in said crests are at a higher.

therethrough in said troughs, said bottom plate elements having perforations therethrough yin said crests, and said perforations in said crests are at a higher level than said perforations in said troughs and the origins of said spirals being at a diierent level from that of the terminations of said spirals.

9. In a bubble column a bubble tray adapted to compensate the thermal expansion and concentration comprising a continuous top plate element and a continuous bottom plate element, said elements being formed to provide a series troughs, said top plate element being superimposed on said bottom plate element so that said crests and troughs are in vertical alignment, said top plate element having perforations therethrough within the area of said troughs, said bottom plate element having perforations therethrough within the area of said crests, and said perforations in said crests are at a higher level than said perforations in said troughs.

EMMETI L. DURRUM. 

